The invention relates to a method for producing of oriented short fiber fleeces or mats as tensile strength cores in compound materials made of fiber suspensions. The apparatus has a screen drum rotating in a container. The screen drum has a removable, permeable film on its drum jacket. The apparatus further includes a suction device for producing a pressure drop inside the screen drum. It also includes a chute for supplying the fiber suspension to the surface of the screen drum.
Such an apparatus is known from German Patent Publication (DE-AS) No. 2,163,799 of same applicant. The method described therein comprises that the circumferential speed of the drum jacket is higher than the supply speed of the suspension, that the fibers are deposited on the permeable film on the drum jacket during multiple revolutions of the drum, whereupon the film is cut off and the fleece or mat built up of unidirectionally oriented fibers is removed from the drum together with the film and dried as well as fixed in a manner known as such. In the apparatus used for this purpose, according to FIG. 3, the first orientation of the short fibers takes place during the flowing in the chute. The important fiber orientation effect, however, is achieved by the transition from the chute to the drum by the acceleration of the fiber suspension due to the higher circumferential speed of the drum jacket relative to the flow on speed.
Tests have shown that the exact orientation of the short fibers has a large influence on the strength characteristics of the fiber fleeces or mats to be produced. However, in the free flowing flow of the supply chute according to German Patent Publication (DE-AS) No. 2,163,799, an orientation is hard to perform. Only in the marginal zones of the chute in which the flow speed increases from zero to the flow speed present in the main portion of the chute, a substantial orientation of the short fibers takes place due to the speed change.